1. Field of the Invention
The present invention relates to an electronic pedometer including a circuit board mounted with an acceleration sensor.
2. Description of the Related Art
A general electronic pedometer is constituted by a control portion such as CPU for carrying out various operations and controls in accordance with a program, a time counting portion including a reference clock signal generator and a dividing/timing circuit, a program storing portion such as ROM stored with the program, a data storing portion such as RAM stored with various data of a step number and the like, inputting means for setting time or switching a mode, LCD for displaying time, a step number or the like, a display driver for driving LCD, and a step number sensor as disclosed in, for example, Japanese Patent Publication No. 3493550 (Patent Reference 1). As the step number sensor of the electronic pedometer, a semiconductor acceleration sensor is representative.
As described above, the general electronic pedometer is a portable electronic apparatus constituted by adding a step number counting function to a portable electronic timepiece, and therefore, the electronic pedometer is provided with various functions other than the step counting function. Representing the functions by display modes, there are a time display mode, a stopwatch mode, a step number mode, a distance mode and the like. The modes are switched by operating an external operating member of a change over switch or the like provided to a pedometer case of an exterior or the like by a user. In the respective modes, the external operating member is operated. For example, in the step number mode, a pitch is changed or the like by operating the external operating member.
Owing to such a structure, the semiconductor acceleration sensor constituting the step number sensor of the electronic pedometer not only detects acceleration by walking of the user but detects an acceleration of the electronic pedometer by operating the external operating member. When the acceleration sensor detects the acceleration of the electronic pedometer by operating the external operating member by the user, the semiconductor acceleration sensor generates an accelerating signal similar to that in a case of detecting the acceleration by walking of the user. The acceleration signal is counted as the step number by being operated to process by the control portion, and therefore, the acceleration of the electronic pedometer by operating the external operating member is counted erroneously as the step number.
Hence, according to the electronic pedometer of a background art disclosed in Patent Reference 1 mentioned above, when the user operates the external operating member, counting of the step number is stopped by a constant time period from when the external operating member is operated, a predicted step number is added to a step number value until stopping to count the step number after the predetermined time period has elapsed, thereby, the step number is made to be proximate to an actual step number. The predicted step number is a step number by which the user is predicted to walk during the predetermined time period and is calculated by, for example, by multiplying an average step number per unit time immediately before stopping to count the step number by the predetermined time period.
In this way, the electronic pedometer of the background art is on a premise that the step number which differs from the actual step number is counted by operating the external operating member, counting of the actual step number is stopped by the constant time period from when the external operating member is operated, and the predicted step number during the stop period calculated by the predetermined operation processing is added to the step number until stopping to count the step number. Therefore, when the external operating member is operated in walking, the electronic pedometer of the background art can display certainly a value proximate to the actual step number. However, the electronic pedometer of the background art adds to process the predicted step number even when the external operating number is operated in stopping to walk, and therefore, there poses a problem that the displayed step number differs from the actual step number. Further, when the external operating member is operated, there is a case in which a walk pitch which differs from the walk pitch until when the pedometer is operated is constituted, however, the predicted step number is not calculated in correspondence with a change in the walk pitch, and therefore, there poses a problem that the displayed step number differs from the actual step number. The problems are caused because the electronic pedometer of the background art is constituted by a structure which cannot count only the actual step number.
Meanwhile, expressing structurally, according to the electronic pedometer of the background art, as shown by FIG. 9 through FIG. 10, a circuit board 10 mounted with an electronic circuit element for executing a signal processing and an acceleration sensor 4 is arranged at inside of a pedometer case 1, and an outer peripheral edge thereof is fixed to the pedometer case 1 by a board fixing portion 6 at two portions through four portions. When an external force is exerted to the pedometer case 1 of such an electronic pedometer, a strain generated the pedometer case 1 is transmitted to the circuit board 10. The strain is propagated to the acceleration sensor, thereby, the acceleration sensor 4 generates a strain detecting signal in response to the strain. The strain detecting signal is processed as a step number signal by the electronic circuit element for signal processing mounted to the circuit board 10 and an erroneous step number which is not the actual step number is counted. The external force is generated also when an unanticipated impact or an excessively large pressure is applied in mounting or detaching the electronic pedometer, or when the electronic pedometer is impacted to something carelessly other than when exerted by operating the external operating member. However, there poses a problem that a method of preventing an erroneous operation of the electronic pedometer by a software as described in Patent Reference 1 is not applicable to such an unanticipated external force.
JP-A-1-287417 (Patent Reference 2) describes an electronic pedometer constituted by attaching a damping member comprising an elastic member to one face of a printed board, attaching one end of an acceleration detecting type sensor comprising a piezoelectric element to the damping member to form the acceleration detecting type sensor as a cantilever, and attaching to a free end of the sensor. According to the electronic pedometer including the step number sensor attached with the acceleration detecting type sensor at the cantilever, up and down rocking of the cantilever generated in accordance with an acceleration of an up and down movement is detected by the acceleration detecting type sensor, thereby, the step number is counted. According to the electronic pedometer having such a unique structure, the acceleration detecting type sensor does not respond to a movement having a high frequency and constituting noise by interposing the damping member. Therefore, the electronic pedometer can prevent an erroneous operation by an external force exerted to the pedometer case and the external force for generating a movement having a high frequency and constituting noise.
However, the electronic pedometer described in Patent Reference 2 needs to use the acceleration detecting type sensor of a special structure, and therefore, there poses a problem that cost is increased by that amount and a size or a shape of the pedometer case is restricted. Further, only a movement having a high frequency and constituting noise can be absorbed by the damping member constituting an indispensable constituent element of the acceleration detecting type sensor of the special structure, and therefore, there poses a problem that the electronic pedometer is erroneously operated when an external force generating the other movement is exerted to the pedometer case.